This invention relates generally to the securing together against relative axial movement of two members in telescopic relation. The members are secured together by a spring ring which is received in cooperating grooves, an internal groove in the external member and an external groove in the internal member.
It is known to have internal and external members as above described in which a spring ring of circular cross section is mounted, for example, in the internal groove of the external member and the free end of the internal member is provided with a chamfer. As the free end is pushed into the external member the chamfer expands the ring and allows the internal member to telescope into the external member until the external groove in the internal member is aligned with the internal groove in the external member whereupon the ring contracts and engages the side walls of both grooves to hold the members against relative axial movement.
In this arrangement the relative dimensions of the grooves and the ring are critical since when the ring is open it must pass over the internal member but when it contracts and is in its closed state it must engage the walls of both of the aligned grooves to hold the members against relative axial movement.
In some applications where greater security is required than is given by a ring of circular cross section, a ring of rectangular section is used, the section normally having a greater dimension radially than axially. When using such a ring it tends to fall to the bottom of the internal groove in the external member and a chamfer on the internal member will not lift the ring nor open the ring when the members are telescoped together. Normally, therefore, such rings have apertured ears at or adjacent their ends and are opened by normal circlip pliers to allow assembly of the members. After assembly the ears are released when the grooves are aligned. In such an arrangement the external groove will have a slot in its base through which the ears will project so as to be accessible to the circlip pliers. In this construction it is again necessary that there is a very specific relation between the dimensions of the ring and of the grooves. The internal groove in the external member must be deep enough to receive the ring completely to allow assembly and the external groove will be less deep.
While in the foregoing we have described the spring ring being held open during assembly of the members, it is equally possible for the spring ring to be held closed during assembly of the members and then released so that it expands into mutually aligned grooves in the members to hold them together. In such a case the external groove in the internal member must be deep enough to receive the ring completely to allow assembly and the internal groove will be less deep.
It has previously been proposed in GB-A- 1 514 690 to have a bridge member which fits into the holes in the ends of a normal circlip and which may be used to hold the circlip open or closed during an assembly operation and then removed to allow the circlip to spring back to its unstressed state. In this arrangement the bridge piece has to be removed in a direction perpendicular to the plane of the circlip and in many assemblies this is not possible.
GB-A-349 329 shows, in FIG. 1, a ring to hold a gudgeon pin in place by engaging in an internal groove in the pin bore. The ring is held in its expanded state by a grooved disc inserted between internally projecting arms on the ring. This arrangement is not suitable for many applications.
Finally, in GB-A-1 137 436 there is shown an arrangement in which an external member has an internal groove which opens through a slot to the exterior of the member and a circlip is used which has long arms which project through the slot into a recess. The circlip can be held by circlip pliers in a closed position during assembly of the members and then allowed to expand to hold the members together. In this case there is no external groove in the internal member. This arrangement is not suitable for use in many applications where there is no access to be able to engage the arms of the circlip with circlip pliers.
In GB-A-1 223 050 there is disclosed an assembly of an external member in telescopic relation with an internal member, the external member having a bore, an internal groove in the bore and a slot extending radially of the bore between an inner end open to the bore and an outer end at the external surface of the external member, the slot extending axially between said groove and an end of the external member. The internal member and the external member are capable of being held in assembled position by a spring ring engaged in said groove and in an external groove of the internal member, the ring having, adjacent its ends, arms which extend generally radially outwardly into said slot. To assemble the members the end portions of the arms, which extend radially outwardly of the slot, have to be drawn together while the parts are telescoped and then released. To enable said end portions to be drawn together it is necessary to have access to the external member during the telescoping operation. In some circumstances, eg. where the external member is itself surrounded by another element, this is not possible and this prior construction is not usable.
In US-A-3 701 303 there is shown, in FIGS. 5 and 6, a stop ring for fitting onto a shaft having a groove. The stop ring has arms on which there are formations which may be engaged by the nipples of pincers for expanding the ring. The pincer nipples may be engaged with and disengaged from the arm formations in directions radially of the ring. Again this arrangement requires radial access to the ring which is not always possible.
Thus in many applications using rings of rectangular section it is not convenient or even possible to use circlip pliers to hold the ring open or closed during assembly of internal and external members either because of the location of the grooves with reference to other parts of an assembly and/or the method of assembly of the members. In these circumstances, none of the known arrangements described above would be suitable for assisting in the assembly of the members.
In such circumstances, therefore, it is necessary to find some means of holding the spring ring open or closed while assembling the members in telescopic relation and then allowing the ring to be released to contract or expand to its normal form when the internal and external grooves are aligned so that the ring engages the walls of both grooves to hold the members in the desired axial position.
It is an object of one aspect of the invention to provide a method of securing together, by means of a spring ring, two members in telescopic relation which may be used in confined situations where the prior art is not usable.
According to this aspect of the invention we provide a method of securing together, by means of a spring ring, an external member in telescopic relation with an internal member, wherein the external member has a bore, an internal groove in the bore and a slot extending radially of the bore between an inner end open to the bore and an outer end at the external surface of the member, the slot extending axially between said groove and an end of the member, and wherein the spring ring is engaged in said groove to locate the internal member and has, adjacent to its ends, arms which extend generally radially outwardly into said slot; characterised in that the internal member has an external groove and in that the method comprises mounting the spring ring in one of said grooves, releasably holding the ring in a contracted or expanded state so that it lies substantially within said one groove by engaging the ring arms with a holding element which is supported wholly by the ring, telescoping the members together while the arms are engaged with the holding element until the grooves in the members are mutually aligned and so that the ring arms and holding element are located in said slot and withdrawing the holding element radially through the outer open end of the slot thus disengaging said arms from the holding element and releasing the ring so that the ring expands or contracts to engage in both of the mutually aligned grooves to secure the members together.
It is an object of another aspect of the invention to provide a telescopic assembly capable of being secured together by the method set forth above.
According to this aspect of the invention we provide a telescopic assembly of an external member and an internal member, wherein the external member has a bore, an internal groove in the bore and a slot extending radially of the bore between an inner end open to the bore and an outer end at the external surface of the member, the slot extending axially between said groove and an end of the member, the members being held in assembled position by a spring ring engaged in said groove and locating the internal member, the ring having, adjacent its ends, arms which extend generally radially outwardly into said slot; characterised in that the internal member has an external groove and the ring engages both of said grooves to hold said members assembled.
It is an object of another aspect of the invention to provide the combination of a spring ring and a holding element which is usable in the method and assembly referred to above.
According to this aspect of the invention we provide the combination of a spring ring of rectangular cross section, the ring having a state of rest in which it is in either an open state or a closed state and has ends adjacent to which are arms which extend generally radially outwardly, with a holding element dimensioned to engage said arms releasably to hold the ring out of its state of rest in a stressed state in which the ring is in either a closed state or open state respectively; characterised in that (1) the holding element has oppositely-facing surfaces which engage generally-radial, oppositely-facing surfaces on the edges of the arms to hold the ring in its stressed state, (2) in that said surfaces on the arms and the holding element can be disengaged by radially outward movement of the holding element relative to the arms and (3) in that the holding element has a part remote from said surfaces whereby it may be gripped.